1. Field of the Invention
This invention relates generally to a device placed in a sewer pipe to trap certain metal articles which may plug the pipe. In particular, this invention relates to a guard with self cleaning features having special applications to toilets in prisons and other correctional facilities.
2. Prior Art
The desirability of providing a guard in a drain pipe or sewer pipe to trap articles which would otherwise clog the pipe has long been recognized in the prior art. With regard to a sewer pipe leading from a toilet, the requirement of a guard is that the ordinary solids introduced into a toilet, such as excrement and tissue paper, should be allowed to pass unobstructed while articles not readily decomposed, such as cloth, diapers, sanitary napkins and plastic, should be trapped. The aforementioned requirement are particularly stringent in the prison setting. Prisoners are prone to introduce cloth and paper into the toilets with the intent that the prison sewage discharge lines become clogged and the sewage water back up so as to overflow into the prisoners' cells. With the present sewage system it is not possible in many cases to determine which prisoner caused the sewage line to become clogged. Hence it is not always possible to punish the prisoner and thereby deter similar future episodes.
Especially damaging is cloth or other material which, even if it does not clog the pipes, is not broken down and passes to the treatment plant where the material can not be digested or properly handled causing the shut down of the treatment plant.
Another problem particular to the prison setting is the need to prevent various metal objects from being flushed through the prison sewage system. In many instances these metal objects will be homemade knives and other weapons that the prisoner is trying to dispose of in order to avoid being caught in possession of these prohibited devices.
Various stationary devices have been employed in sewer lines to trap undesirable articles as shown in the following U.S. patents.
______________________________________ Lehmann 2,693,603 Click et al. 2,811,724 Sierzega 3,904,523 Halstad 4,307,476 ______________________________________
Several of these inventions disclose devices with hooks which are positioned in the sewer line. However, because these devices are stationary, there is a tendency for otherwise safe waste, especially toilet paper, to accumulate on the hooks. Eventually, the line plugs at the site of the guard device. Also since these devices are not operationally activated by the flushing of a toilet they would not in all cases be useful in determining from which toilet (and corresponding prisoner) was responsible for introducing the material into the sewage line.
Devices which rotate within a pipe to scrape the interior of the pipe or pulverize solids have been employed with some success. Examples of rotating guards may be found in the following U.S. patents.
______________________________________ Hirrich 1,217,763 Peaden 2,454,884 Hirshstein 2,627,610 Moore 3,439,361 ______________________________________
In a prison setting, however, where material and garments are introduced into the sewage system, additional burdens are placed upon the comminuting devices. For example, even the most powerful in line device disclosed in the prior art would have difficulty pulverizing a bed sheet. In addition they would not be able to prevent the passage of certain metal objects that are commonly made by prisoners and used as weapons.